Riding lawn mower tractor



FIG. 1 is a perspective view of a riding lawn mower tractor, showing our new design;

FIG. 2 is a right side elevational view thereof, the motor shown in broken lines is for illustrative purposes only, and forms no part of the claimed design;

FIG. 3 is a left side elevational view thereof;

FIG. 4 is a front elevational view thereof;

FIG. 5 is a rear elevational view thereof; and

FIG. 6 is a top plan view thereof. 

The ornamental design for a riding lawm mower tractor, as shown and described. 